JP2010028464A - Communication system and transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the communication which does not go through a representative device from stop working when there occurs a failure in the representative device of a broadcast subnetwork using a link-state for routing, and to shorten the time until switching the communication path of the communication via the representative device to the other device on the subnetwork. <P>SOLUTION: Both the representative device 11 and the other alternative representative device 12 selected generate link state information about the subnetwork about the broadcast subnetwork. All transfer devices 11 to 13 connected to the subnetwork are configured to include the link to both the link-state information about the subnetwork generated by the respective representative device 11 and the alternative representative device 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a communication system and a transfer device, and in particular in a broadcast subnetwork that uses a link state for routing, when a failure occurs in a representative device, communication that does not pass through the representative device is not stopped. The present invention relates to a communication system and a transfer device for quickly switching a communication path of communication passing through.

In a conventional link state type routing protocol, when a plurality of transfer devices such as routers exist on a broadcast network, one representative transfer device (representative device) is selected. The representative device once collects route information to be exchanged in the broadcast subnetwork and reliably redistributes the route information to each transfer device. The representative device generates and advertises connection information with the transfer device as seen from the network instead of the network.
As a conventional technique, as shown in Non-Patent Document 1, etc., as a typical link state type routing protocol for selecting a representative device or an alternative representative device that is a transfer device that replaces the representative device in a broadcast subnetwork. There is an OSPF (Open Shortest Path First).
When a failure occurs in the representative device, another transfer device becomes the representative device and continues the function of the representative device. Between the occurrence of a failure in the representative device and the replacement transfer device taking over the function of the representative device, the path information exchange stops, and the link state information about the broadcast network becomes invalid as a node on the topology. For the exchange of route information, there is a method in which an alternative representative device is placed in addition to the representative device so that the function continues without interruption even if a failure occurs in the representative device. However, no method has been proposed in the past to keep link state information about a broadcast network valid.

Internet Engineering Task Force, RFC 2328, “OSPF Version 2”

In the present invention, in view of the above points, when a failure occurs in a representative device of a broadcast subnetwork that uses a link state for routing, the link state information about the broadcast subnetwork becomes invalid, and thus does not pass through the representative device. One of the purposes is to prevent communication from being stopped.
Another object of the present invention is to shorten the time required to switch the communication path of communication via the representative device to another transfer device on the broadcast subnetwork.

In the broadcast subnetwork, an alternative representative device is prepared in addition to the representative device, and the two transfer devices respectively generate link state information for the subnetwork.
In all transfer devices connected to the sub-network including the representative device and the substitute representative device, the link state information generated by each transfer device includes a link to the link state information for the sub-network generated by the representative device, and the substitute device Include both links in the link state information for the subnetwork generated by the representative device.
When a failure occurs in the representative device and the link state information about the subnetwork generated by the representative device becomes invalid, or the link about the subnetwork generated by the representative device included in the link state information generated by each device When the link to the state information becomes invalid, the link state information about the subnetwork generated by the alternative representative device and the subnetwork generated by the alternative representative device included in the link state information generated by each transfer device Communication between the sub-networks excluding the representative device can be maintained by the link to the link state information.

According to the first solution of the present invention,
A communication system comprising a plurality of transfer devices connected to a network and using link states for routing,
The transfer device selected as the representative device generates the first network link state information about the network, and transmits the generated first network link state information.
The transfer device selected as the substitute representative device generates second link state information about the network, transmits the generated second network link state information,
The representative device, the substitute representative device, and one or a plurality of transfer devices other than the representative device or the substitute representative device are the first and second network devices generated by the substitute representative device and the representative device, respectively. Generate both device and link state information about the device, including both links to the link state information, and send the generated device and link state information.
One or a plurality of transfer devices other than the representative device or the substitute representative device hold the received first and second network link state information and a plurality of the device / link state information,
When the communication path between the representative device or the representative device and the network fails, one or a plurality of transfer devices other than the representative device or the alternative representative device receive the second network link state received from the alternative representative device. The communication system is provided in which a link state information connection between transfer devices on the network excluding the representative device is maintained using a link to information.

According to the second solution of the present invention,
A transfer device in a communication system comprising a plurality of transfer devices connected to a network and using link states for routing,
When the transfer device is selected as a representative device, the transfer device generates first network link state information about the network, and transmits the generated first network link state information.
When the transfer device is selected as the substitute representative device, the transfer device generates second link state information about the network, and transmits the generated second network link state information.
The representative device, the substitute representative device, and one or a plurality of transfer devices other than the representative device or the substitute representative device are the first and second network devices generated by the substitute representative device and the representative device, respectively. Generate both device and link state information about the device, including both links to the link state information, and send the generated device and link state information.
One or a plurality of transfer devices other than the representative device or the substitute representative device hold the received first and second network link state information and a plurality of the device / link state information,
When the communication path between the representative device or the representative device and the network fails, one or a plurality of transfer devices other than the representative device or the alternative representative device receive the second network link state received from the alternative representative device. The transfer device is provided that uses a link to information to maintain a link state information connection between transfer devices on the network excluding the representative device.

According to the present invention, when a failure occurs in a representative device of a broadcast subnetwork that uses a link state for routing, link state information about the broadcast subnetwork becomes invalid, and communication that does not pass through the representative device is stopped. Can be prevented.
Further, according to the present invention, it is possible to shorten the time until the communication path of communication via the representative device is switched to another device on the broadcast subnetwork.

The best mode for carrying out the present invention will be described with reference to the drawings.

1. Hardware Configuration FIG. 1 is a network configuration diagram (1).
The illustrated network includes, for example, transfer apparatuses 11, 12, 13, and 14 and a broadcast subnetwork 21.
The transfer devices 11, 12, and 13 are connected to the broadcast subnetwork 21, for example. For the routing, for example, a link state protocol such as OSPF is used. The transfer devices 11, 12, and 13 select a representative device and an alternative representative device for the broadcast subnetwork 21 from among the transfer devices 11, 12, and 13. A method for selecting the representative device and the alternative representative device will be described later. For the sake of explanation, for example, the representative device is assumed to be the transfer device 11 and the alternative representative device is assumed to be the transfer device 12. The transfer device 11, which is a representative device, generates link state information for the broadcast subnetwork 21. A method for generating link state information for the broadcast subnetwork will be described later.

FIG. 19 is a block diagram illustrating a configuration of the transfer apparatus.
As illustrated, the transfer device includes, for example, a control unit 100 and a communication unit 110. For example, the control unit 100 includes a CPU 101 and a memory 102. When the CPU 101 executes a program stored in the memory 102, the entire apparatus is managed and packet processing is performed. The program stored in the memory 102 includes a routing processing unit 103. The routing processing unit 103 includes a routing table 104. A detailed configuration of the routing processing unit 103 will be described later. The communication unit 110 includes a transfer unit 111 and a network interface 112, for example. The network interface 112 includes a port 113, for example. The network interface 112 performs packet transmission / reception via the port 113, for example. In the figure, there are only two ports 113 in the network 112 as an example, but there may be more ports. Also, as an example, there are only two networks 112 as well, but there may be more. A packet received from the port 113 is transmitted from an appropriate port 113 after the transmission unit 111 determines a transmission port. A routing protocol control packet and the like are processed by the routing processing unit 103 of the control unit 100. Details of appropriate port selection processing and routing protocol control packet processing will be described later.

FIG. 20 is a configuration diagram illustrating an internal block of the routing processing unit of the transfer apparatus.
The routing processing unit 103 includes, for example, a routing table 104, a reception processing unit 120, a transmission processing unit 121, an adjacency management unit 122, a link state database 123, a route calculation unit 124, and a link state information generation unit 125. Prepare. The link state database 123 includes, for example, link state information 30 about a network to be described later and link state information 50 about its own device.

FIG. 24 is an explanatory diagram of link state information regarding the network.
The link state information 30 about the network includes, for example, generated transfer device information 40, protocol-specific information 41, and transfer device information 42 connected to a certain subnetwork. The protocol-specific information 41 includes, for example, adjacent transfer device information stored in the adjacent management unit 122, interface address information used in the routing protocol, and route information set in the routing table 104 by another routing protocol. Can be included. Adjacent transfer device information can be used, for example, address information or device identification information of adjacent transfer devices. As the route information, for example, the cost in OSPF can be used.

FIG. 2 is an explanatory diagram of link state information about the broadcast subnetwork 21 generated by the transfer device 11 as the representative device.
The link state information 31 includes, for example, information that the transfer apparatuses 11, 12, and 13 are connected to the broadcast subnetwork 21. The link state information 31 is distributed to the transfer devices 12 and 13 by the transfer device 11.
FIG. 25 is an explanatory diagram of link state information about the own device.
The link state information 50 about the device itself is stored in the link state database 123.
The link state information 50 about the own device includes, for example, the generated transfer device information 40, protocol-specific information 41, and link information 43.

FIG. 3 is an explanatory diagram (1) of the link state information about the own device generated by the transfer device 11.
FIG. 4 is an explanatory diagram (1) of the link state information about the own device generated by the transfer device 12.
FIG. 5 is an explanatory diagram (1) of the link state information about the own device generated by the transfer device 13.
The link state information 51, 52, 53 includes, for example, a link to the link state information 31 in the link information, and the transfer device 13 uses the information to communicate with the device 11 and the device via the broadcast subnetwork 21. 12 can be recognized.
The link state information about the own device and the link state information about the network can be mutually converted and stored by the transfer devices 11, 12, and 13 connected to the sub-network 21 and the like.

2. Failure Detection by Transfer Device Other than Alternative Representative Device (1) Related Technology First, the related technology of this embodiment will be described.
FIG. 6 is an explanatory diagram (1) showing data transfer in the network.
As illustrated, the transfer devices 11 and 12 are further connected to the transfer device 14, and communication between the transfer devices 13 and 14 is performed via the transfer device 11.
Here, for example, in the network configuration of FIG. 1, when a failure occurs between the transfer device 11, which is a representative device, and the broadcast subnetwork 21, and the transfer device 13 detects it, the own device generated by the transfer device 13 The link from the link information 43 of the link state information 53 to the link state information 31 is deleted.

FIG. 7 is an explanatory diagram (2) of the link state information generated by the transfer device 13.
The link state information 54 indicates the link state information 50 about the own device generated by the transfer device 13 when the transfer device 13 detects the above-described failure.
FIG. 8 is an explanatory diagram (1) showing data transfer when a failure occurs in the broadcast network.
As shown in the figure, the transfer device 13 deletes the link state information 31 from the link state information 54 for the own device, so that the transfer device 13 loses reachability to the broadcast subnetwork 21. Therefore, communication between the transfer devices 13 and 14 is stopped. Thereafter, when the transfer device 12 that is the substitute representative device detects a failure, the transfer device 12 that is the substitute representative device becomes the representative device for the broadcast subnetwork 21 and generates link state information for the broadcast subnetwork 21.
FIG. 9 is an explanatory diagram of link state information about the network generated by the transfer device 12 which is an alternative representative device.
The link state information 32 indicates link state information about the broadcast subnetwork 21 generated by the transfer device 12. The link state information 32 is distributed to the transfer device 13 by the transfer device 12.

FIG. 10 is an explanatory diagram (3) of the link state information about the own device generated by the transfer device 13.
The link state information 55 indicates link state information about the own device that is generated when the transfer device 13 receives the link state information 32 about the network. The link state information 55 about the own device includes link information 42 to the link state information 32 about the network created by the transfer device 12 in the link information 42.
FIG. 11 is an explanatory diagram (1) illustrating data transfer in which a communication path is switched when a failure occurs in the broadcast network.
The transfer device 12 or 13 performs route calculation using the link state information 32 about the network and the link state information 55 about the own device, so that the transfer device 13 passes through the broadcast subnetwork 21 as shown in the figure. You can communicate. Then, communication between the transfer devices 13 and 14 is restored using the transfer device 12 as a communication path. That is, in the related technology of the present embodiment, communication is stopped from the occurrence of a failure until the new representative device performs its function.

(2) Embodiment Next, a case where the present embodiment is applied to the same network configuration as described above will be described.
In the present embodiment, the transfer device 12 that is an alternative representative device also generates link state information for the broadcast subnetwork 21 in advance before the occurrence of a failure.
The link state information 32 illustrated in FIG. 9 indicates link state information regarding the broadcast subnetwork 21 generated by the transfer device 12. The link state information 32 includes information indicating that the transfer devices 12 and 13 are connected to the broadcast subnetwork 21 in addition to the transfer device 11 that is the representative device, and the transfer device 11 that is the representative device is connected. This information is not included. The link state information 32 regarding the broadcast subnetwork 21 is distributed to the transfer apparatuses 11 and 13 by the transfer apparatus 12.
FIG. 12 is an explanatory diagram (2) of the link state information about the own device generated by the transfer device 11.
FIG. 13 is an explanatory diagram (2) of the link state information about the own device generated by the transfer device 12.
FIG. 14 is an explanatory diagram (4) of the link state information about the own device generated by the transfer device 13.

The link state information 56, 57, 58 for the own device includes a link to the link state information 32 for the network as well as a link to the link state information 31 for the network.
For example, when a failure occurs between the transfer device 11 and the broadcast subnetwork 21 and the transfer device 13 detects the failure, the link state information 31 about the network is generated from the link state information 58 about the own device generated by the transfer device 13. The link to is deleted. At this time, the link state information is the same as the link state information 55 for the own device generated by the transfer device 13 as shown in FIG.
At this time, the transfer device 13 maintains the reachability to the broadcast subnetwork 21 by using the link state information 32 about the network previously generated by the transfer device 12 which is an alternative representative device. After the route calculation by the transfer device 13, the route connected to the transfer device 14 via the transfer device 12 is restored as the communication path. In other words, in this embodiment, even if a failure occurs in a representative device of the network, reachability to the network is not lost, so that the time until path switching can be shortened compared to the related technology of this embodiment. it can.

3. Fault Detection by Alternative Device (1) Related Technology First, the related technology of this embodiment will be described.
FIG. 15 is a network configuration diagram (2).
The illustrated network includes, for example, transfer apparatuses 11, 12, 13, 14, and 15 and a broadcast subnetwork 21.
FIG. 16 is an explanatory diagram (2) showing data transfer in the network.
As illustrated, the transfer apparatuses 11, 12, and 13 are connected via a broadcast subnetwork 21. The transfer devices 11 and 12 are further connected to the transfer device 14. The transfer devices 13 and 14 are connected to the transfer device 15, respectively. Communication between the transfer devices 13 and 14 is performed via the transfer device 11 as a communication path.
A description will be given taking the illustrated network as an example.

FIG. 17 is an explanatory diagram (2) showing data transfer when a failure occurs in the broadcast network.
For example, when a failure occurs between the transfer device 11 and the broadcast subnetwork 21 and the transfer device 12 as an alternative representative device first detects the failure, the transfer device 13 has not yet detected the failure. The communication path for communication between the devices 13 and 14 continues via the transfer device 11.
However, in such a case, since the transfer device 13 cannot actually communicate via the transfer device 11, the communication between the transfer devices 13 and 14 stops.
FIG. 18 is an explanatory diagram (2) showing data transfer in which the communication path is switched when a failure occurs in the broadcast network.
As described above, for example, when a failure occurs between the transfer device 11 and the broadcast subnetwork 21 and the transfer device 13 detects a failure after the communication between the transfer devices 13 and 14 is stopped, the transfer device 13 reroutes again. Calculation is performed, and the transfer path 15 is restored as a communication path as shown in the figure. That is, in the related technology of the present embodiment, communication is stopped from the occurrence of a failure until each transfer device detects the failure.

(2) Embodiment Next, a case where the present embodiment is applied to the same network configuration as described above will be described.
For example, when a failure occurs between the transfer device 11 and the broadcast subnetwork 21 and the transfer device 12 as an alternative representative device first detects it, the transfer device 12 becomes the representative device for the broadcast subnetwork 21. At that time, the transfer device 12 notifies the transfer device 13 of a deletion notification of the link state information 31 for the broadcast subnetwork 21 generated by the transfer device 11. When the transfer device 13 receives the deletion notification, the transfer device 13 deletes the link state information 31 about the network generated by the transfer device 11 from the link state database 123. The transfer device 13 includes link state information 32 about the broadcast subnetwork 21 generated by the transfer device 12. However, in the information of the link state information 32 for the broadcast subnetwork 21, the transfer device 11 is not connected to the broadcast subnetwork 21 because the transfer device information 42 is not included in the connected transfer device information 42. Therefore, even if the transfer device 13 does not detect a failure of the transfer device 11, communication with the broadcast subnetwork 21 is stopped. That is, when the route calculation is performed by the transfer device 13, the route calculation is performed using the link state information 32 about the broadcast subnetwork 21, and therefore, the route through the transfer device 15 can be restored as a communication path.
That is, in the present embodiment, communication is stopped from the occurrence of a failure until any of the transfer devices or the alternative representative device detects the failure. However, in the related technology, communication is not recovered unless the own device detects a failure. However, in this embodiment, communication is restored even if the substitute representative device detects a failure before the own device detects the failure. Therefore, this embodiment can shorten the time until the path is switched as compared with the related art.

4). Detailed Operation A detailed operation of the present embodiment will be described.
The link state routing protocol mainly includes an adjacency monitoring function, a database synchronization function, a route calculation function, and the like. The adjacency monitoring function is a function that mainly detects a transfer device connected to the device itself or through a switch or the like by periodically transmitting and receiving protocol control packets and monitoring the connection maintenance state. The database synchronization function mainly creates a link state information 50 for its own device and transmits it to a transfer device detected by the adjacency monitoring function, and a network received from an adjacent device (including devices connected to a subnetwork). The link state information 30 and the link state information 50 about the device itself are stored in the link state database 123. The route calculation function is a function that performs route calculation based on the link state database 123 and sets a route in the routing table 104.

(1) Adjacency monitoring function The adjacency monitoring function will be described.
In the example of FIG. 1, there are three transfer apparatuses 12, 13, and 14 adjacent to the transfer apparatus 11. Similarly, three transfer devices are adjacent to the transfer device 12. On the other hand, the transfer devices adjacent to the transfer device 13 are two transfer devices 11 and 12. The number of transfer devices 14 is also two. The routing processing unit 103 of each transfer device periodically transmits a protocol control packet (for example, a Hello packet in OSPF) from the transmission processing unit 121 to an adjacent transfer device. This protocol control packet is used, for example, for other transfer devices to detect this transfer device and monitor its connection maintenance state. On the other hand, protocol processing packets from other transfer devices are received by the reception processing unit 120. The received protocol control packet is checked by the adjacency manager 122. (For example, the adjacency management unit 122 can execute the check by comparing the Router ID of the Hello packet with a table for managing adjacent transfer devices such as a neighbor table in OSPF stored in the adjacency management unit 122. At this time, for example, it can be confirmed that the Router ID of the Hello packet matches the address information of each transfer device managed by the neighbor table, etc.) The transfer already recognized by the received protocol control packet If it is determined that the protocol control packet is received from the device, the adjacency management unit 122 updates information about the transfer device. (For example, the adjacency management unit 122 can update the address information and the like for the corresponding other transfer device to the address information and the like included in the received protocol control packet.)

On the other hand, in the case of a protocol control packet received from a transfer device that has not yet been recognized, the adjacency management unit 122 performs processing for starting the establishment of the adjacency state. (For example, the adjacency management unit 122 transmits a Hello packet including the address information of the transfer device to the other transfer device from the transmission processing unit 121, and exchanges the address information and the like with the other transfer devices. The adjacency state can be established with another transfer device.) Note that, when the protocol control packet is not received from the transfer device that is the adjacent device for a certain period of time, the adjacency management unit 122 has detected a failure in the transfer device. It is considered. In the case of a broadcast subnetwork, each transfer device selects a representative device of the subnetwork and, if necessary, an alternative representative device. A method of selecting the representative device and the alternative representative device will be described later.
Note that the time for transmitting a protocol control packet at regular intervals and the time for not considering receiving a protocol control packet for a certain period of time are considered to be the occurrence of a failure in advance. Can be set to
Hereinafter, the adjacency monitoring function will be described with the transfer apparatuses 11 and 12 of FIG. 1 as an example.
The transfer device 11 transmits a protocol control packet from each interface connected to the broadcast subnetwork 21 and the transfer device 14. The transfer device 12 performs the above-described check on these protocol control packets received from the network interface 112 connected to the broadcast subnetwork 21 via the port 113. Specifically, for example, if the information (for example, address information) of the transfer device 11 is not registered in the adjacent management unit 122 of the transfer device 12, the transfer device 12 stores the transfer device 11 in the adjacent management unit 122. Register information. (Specifically, for example, the transfer device 12 manages the address information of the transfer device 11, the address information of the network interface 112 of the transfer device 12 determined by the transfer unit 111 for transmitting and receiving protocol control packets, etc.) On the other hand, if the information on the transfer device 11 is already registered in the adjacency management unit 122 of the transfer device 12, the transfer device 12 transfers the transfer device 11 registered in the adjacency management unit 122. Is updated to the information of the transfer apparatus 11 that has been newly received. The information on the transfer device 11 registered in the adjacent management unit 122 of the transfer device 12 is deleted from the adjacent management unit 122 unless it is updated for a certain period of time. That is, the transfer device 11 is not regarded as a transfer device adjacent to the transfer device 12. The transfer device 12 can recognize that a failure has occurred in the connection between the transfer device 11 and the broadcast subnetwork 21 by deleting the information of the transfer device 11 from the adjacent management unit 122 of the transfer device 12.

(2) Selection of Representative Device and Alternative Representative Device A method for selecting a representative device and an alternative representative device among the adjacent monitoring functions will be described.
The adjacency management unit 122 holds identifiers of representative devices, alternative representative devices, and other transfer devices in each subnetwork (for example, address information of each transfer device). (Specifically, for example, the adjacency management unit 122 can obtain the identifiers of the representative device and the alternative representative device from the Designated Router and the Backup Designated Router included in the Hello packet. The identifier of each transfer device can be obtained from the transfer device information 40 generated by the link state information 50 for the own device created by each transfer device, and the identifier of the representative device and the identifier of the alternative representative device are: For example, in FIG. 1, the transfer device 13 is connected to the transfer devices 11 and 12 via the broadcast subnetwork 21. The transfer device 11 is a representative device. Manages information of the transfer device 12 is an alternative representative device. The protocol control packet transmitted / received between the transfer apparatuses includes a representative apparatus determination priority (for example, Router Priority) of the transfer apparatus (or its interface) that transmitted the protocol control packet, and a transfer that transmitted the protocol control packet. The identifier of the transfer device selected by the device as the representative device or the alternative representative device (for example, Designated Router, Backup Designated Router) is included.

OSPF is a typical link state protocol for selecting a representative device and an alternative representative device for a subnetwork.
In OSPF, a representative device and an alternative representative device for a subnetwork are determined as follows. First, each transfer device calculates a new alternative representative device. Only a transfer device that has not selected its own device as a representative device from the information of the protocol control packet can be an alternative representative device. (For example, each transfer device determines whether the transfer device that has transmitted the Hello packet is the transfer device that has selected itself as the representative device by comparing the Router ID of the received Hello packet with the Designated Router. If there is a transfer device that has selected its own device as an alternative representative device among the transfer devices that have not selected that own device as the representative device, the representative device determination priority (for example, Router Priority) The transfer device with the highest () is the substitute representative device. If the priorities are the same, a transfer device having a large transfer device identifier (for example, transfer device address information) is selected. If there is no transfer device that has selected its own device as the substitute representative device, the transfer device with the highest representative device decision priority is set as the substitute representative device. When the priorities are the same, the transfer device having the largest identifier is selected based on the identifier of the transfer device (for example, address information of the transfer device).
Each transfer device then calculates a new representative device. If there is one or more transfer devices that have selected their own device as the representative device from the protocol control packet information, the transfer device with the highest representative device determination priority is set as the representative device. If the priorities are the same, a transfer device having a large transfer device identifier is selected. If there is no transfer device that has selected its own device as the representative device, the recently selected alternative representative device is set as the representative device. (For example, when the protocol control packet is received from a certain transfer device, if the representative device determination priority of the own device or the identifier of the transfer device is larger, the received protocol control packet is discarded and the transfer device of the transmission source On the other hand, a new representative device can be selected by newly transmitting a protocol control packet.) Each transfer device performs these selection processes until an alternative representative device and a representative device for a subnetwork are selected. Execute. Each transfer device can perform a selection process of these representative devices and alternative representative devices by a protocol control packet exchanged when the adjacent state is established. In addition, the address of the transfer device selected as the representative device or the alternative representative device may be stored in the adjacent management unit 122. The representative device determination priority and the transfer device identifier can be set in advance for each transfer device.

(3) Database synchronization function The database synchronization function will be described below. The link state information generating unit 125 generates the link state information 50 for the device itself. The generated information includes the adjacent transfer device recognized by the adjacency management unit 122, the address information of the interface used in the routing protocol, the route set in the routing table 104 by another routing protocol, and the like. (The link state information generation unit 125 can obtain, for example, address information of adjacent transfer devices and address information of the network interface 112 that communicates with each adjacent transfer device from the adjacency management unit 122. Also, link state information. For example, the generation unit 125 can acquire, from 124, route information (including costs and the like) to the adjacent transfer device calculated by the route calculation unit 124. The link state information generation unit 125 can acquire these pieces of information. Thus, the protocol specific information 41 can be created, and when the link state information 30 about the network is stored in the link state database 123, the link state information generating unit 125, for example, the link state information about the network Link to 30 The link state information generating unit 125 can create the link state information 50 for the own device based on the information of the own transfer device information 40, the protocol specific information 41, and the link information 43. )
When the own device is selected as the representative device by the adjacency management unit 122, the link state information 30 for the subnetwork is also generated. (The link state information generation unit 125, for example, each information of the adjacent transfer device of the “generated transfer device information” 40 or the protocol specific information 41 included in the link state information 50 for the own device created by each transfer device. Thus, the address information of each transfer device can be set to “connected transfer device information” 42. The link state information generation unit 125 creates the link state information 30 for the network based on the information. can do.)

The link state information generation unit 125 holds the generated link state information 50 about the device itself and / or link state information 30 about the network in the link state database 123. Since the link state information 30 about the network includes information on the adjacent transfer device, for example, when the adjacent management unit 122 detects a failure in the adjacent transfer device, the adjacent management unit 122 indicates that the failure has been detected in the link state. The information generation unit 125 is notified. The link state information generation unit 125 that has received the notification that a failure has been detected regenerates the link state information 30 about the network and stores it in the link state database 123.
The link state information 50 for the own device and / or the link state information 30 for the network in the link state database 123 is transmitted to another transfer device by the transmission processing unit 121.
On the other hand, the reception processing unit 120 receives link state information from other transfer apparatuses. The reception processing unit 120 checks whether the received link state information 50 about the own device and / or the link state information 30 about the network is received from the transfer device recognized by the adjacency management unit 122. In the case of the link state information 50 and / or the network link state information 30 received from the adjacent transfer device, the adjacency management unit 122 receives the link state information 50 and / or the network information about the received device. The link state information 30 is held in the link state database 123. On the other hand, if the link state information 50 and / or the network link state information 30 received from the adjacent transfer device is not the adjacency management unit 122, the adjacency management unit 122 receives the link state information 50 and / or the network regarding the received own device. The link state information 30 on is discarded.

Hereinafter, the database synchronization function will be described by taking the transfer device 13 and the link state information 31, 32, 51 to 53 of FIG. 1 as an example.
The transfer device 13 includes two types of links in the link state database 123: link state information 51, 52, 53 for the own device generated by each transfer device and link state information 31 for the broadcast subnetwork 21 generated by the representative device. It holds state information. Further, link state information 32 about the broadcast subnetwork 21 generated by the alternative representative device is also stored in the link state database 123. The transfer device 13 is information from the transfer device 11 or 12 based on the two types of link state information described above, that is, the generated transfer device information 40 included in each of the link state information 51 and 52 and the link state information 31. This is confirmed by the reception processing unit 120. In addition, the adjacency management unit 122 confirms that the transfer apparatuses 11 and 12 are transfer apparatuses adjacent to the transfer apparatus 13. (Specifically, for example, the adjacency management unit 122 generates the generated transfer device included in the received link state information 51, 52, 53 of the own device and the link state information 31 for the broadcast subnetwork 21 generated by the representative device. (By comparing the address information of the information 40 with the address information of the adjacent transfer device stored in the adjacency management unit 122, it is possible to confirm whether it is an adjacent transfer device.)

(4) Route Calculation Function The route calculation function will be described below.
Based on the link state information 30 about the network and the link state information 50 about the own device held in the link state database 123, the route calculation unit 124 sends information to each destination (address information of the transfer device to be finally delivered). Calculate the route. As for the route calculation method, for example, the shortest route is determined using an appropriate method such as the Dijkstra algorithm. The route calculation unit 124 sets a calculation result (for example, address information and route information (for example, cost) of the next transfer device for each destination) in the routing table 104. When there is a change in the contents of the link state database 123, the route calculation unit 124 performs route calculation again based on the updated link state information 30 for each network, link state information 50 for its own device, and the like. The contents of the routing table 104 are used when the transfer unit 111 determines a packet destination. For example, the transfer unit 111 compares the address of the received data with the address information of the transfer device of each destination stored in the routing table 104, and acquires the address information of the next transfer device corresponding to the matching address information. Determine the appropriate network interface 112 and port 113.
Hereinafter, the path calculation function will be described by taking the transfer device 13 and the link state information 31, 32, 51 to 53 of FIG. 1 as an example.

Based on the link state information 31 for the broadcast subnetwork 21 generated by the representative device and the link state information 51, 52, 53 for the own device created by each transfer device, the route calculation unit 124 of the transfer device 13 calculates the route. Execute. The link state information 32 about the broadcast subnetwork 21 generated by the alternative representative device is not used for route calculation while the route calculation unit 124 uses the link state information 31 generated by the representative device. When the transfer device 13 detects a failure of the transfer device 11 and deletes the information of the transfer device 11 from the adjacency management unit 122, the route calculation unit 124 uses the broadcast subnetwork 21 generated by the transfer device 11 in the link state database 123. The link state information 31 is no longer used for route calculation. Since a failure has occurred in the transfer device 11 that is the representative device, the route calculation unit 124 uses the link state information 32 for the broadcast subnetwork 21 created by the alternative representative device instead of the link state information 31 created by the representative device. Performs route computation.
When the transfer device 12 detects a failure of the transfer device 11, the transfer device 12, which is an alternative representative device, transmits another notification that the link state information 31 generated by the transfer device 11 is deleted to the broadcast subnetwork 21. Transmit to a device (for example, transfer device 13). Even when the transfer device 13 receives the deletion notification by the reception processing unit 120, the transfer device 13 deletes the information of the transfer device 11 from the adjacent management unit 122, and the route calculation unit 124 stores the information in the link state database 123. Stop using link state information 31 for a certain broadcast subnetwork 21 for route calculation. Then, as described above, the route calculation unit 124 performs route calculation based on the link state information 32 for the broadcast subnetwork 21.

(5) Operation when receiving link state information about network FIG. 21 is an operation flowchart when the transfer apparatus receives link state information about the network.
The reception processing unit 120 receives the link state information 30 about the network (2100). The reception processing unit 120 notifies the adjacency management unit 122 of link state information about the received network, and the adjacency management unit 122 checks whether the transfer device that generated the link state information about the network is a representative device ( 2101) When the transfer device that generated the link state information about the network is a representative device, the adjacency management unit 122 holds the received link state information about the network in the link state database 123 (2106). In the example of FIG. 1, the link state information generation unit 125 corresponds to the link state information 31 about the network. The own device generates link state information about the own device in the link state information generation unit 125, and at that time, the link state information generation unit 125 uses the link state information about the network held in the link state database 123 as the link information 43. Include (2102). On the other hand, if the transfer device that generated the link state information 30 for the network is not the representative device in step 2101, the adjacency management unit 122 checks whether the transfer device that generated the link state information 31 is an alternative representative device ( 2103). When the transfer device that generated the link state information 30 for the network is an alternative representative device, the adjacency management unit 122 stores the link state information 31 for the network in the link state database 123 (2107). In the example of FIG. 1, it corresponds to the link state information 32 about the network. The link state information generation unit 125 generates the link state information 50 for the own device, and at this time, the link state information 32 about the network held in the link state database 123 is included in the link information 43 (2104). In step 2103, if the transfer device that generated the link state information for the network is not the substitute representative device, the adjacency manager 122 does not hold the link state information for the network in the link state database 123 (2108). When the link state information generating unit 125 generates link state information about the own device, the link state information generating unit 125 includes the link state information not stored in the link state database 123 in the link information 43. No (2105).
According to the flowchart as described above, in the example of FIG. 1, the link state information for the own device in which the link state information of the representative device and the alternative representative device is held corresponds to the link state information 58 for the own device.

(6) Operation when selected as an alternative representative device)
FIG. 22 is a flowchart when the own device is selected as the substitute representative device.
When the reception processing unit 120 receives the protocol control packet, the adjacency management unit 122 performs an alternative representative device selection process based on the representative device determination priority and the transfer device identifier according to the above-described procedure (2200). The adjacency management unit 122 determines whether the own device is an alternative representative device from the result of the step 2200 (2201). In step 2201, when the own device is selected as the substitute representative device, the routing processing unit 103, in addition to the processing conventionally performed as the link state protocol, the link state information generating unit 125 displays the link state information about the network. Generate (2202). In the example of FIG. 1, it corresponds to the link state information 32 about the network. The link state information about the generated network is held in the link state database 123 (2203). The link state information for the network generated in step 2202 is transmitted by the transmission processing unit 121 to another transfer device connected to the sub-network (2204).
On the other hand, if the own device is not selected as the alternative representative device in step 2201, the routing processing unit 103 performs only the processing conventionally performed as the link state protocol (2205).

(7) Operation when Selected as Representative Device FIG. 23 is a flowchart when the own device detects a failure of the representative device and becomes the representative device.
The adjacent management unit 122 detects the failure of the representative device. For example, when the adjacent management unit 122 does not receive a packet from the representative device for a certain period, it detects a failure in the representative device. Since the link state information for the network generated by the representative device becomes invalid in the link state database 123 when the failure is detected, the adjacency managing unit 122 displays the link state information for the network generated by the representative device in the link state database. It is deleted from 123 (2300). In the example of FIG. 1, it corresponds to the link state information 31 about the network. In step 2300, the adjacency management unit 122 performs representative device selection processing based on the representative device determination priority and the identifier of the transfer device according to the above-described procedure (2301). The adjacency management unit 122 determines whether the own device is a representative device from the result of Step 2301 (2302). In step 2302, when the own device becomes a new representative device, the routing processing unit 103 deletes the link state information 31 for the subnetwork previously generated and advertised by the representative device in the link state information generation unit 125. Data is generated (2303). For example, the link state information generation unit 125 creates data having an identifier of the previous representative device and information indicating that the link of the previous representative device is deleted. The data to be deleted is transmitted by the transmission processing unit 121 to another transfer device connected to the subnetwork (2304).
On the other hand, if it is determined in step 2302 that the device itself is not a representative device, the routing processing unit 103 ends the processing.

The present invention can be applied to a network such as a broadcast subnetwork that uses a link-state protocol for routing.
The present invention is not limited to a broadcast subnetwork, but can be applied to various subnetworks and various networks.

Network configuration diagram (1). Explanatory drawing of the link state information about the broadcast subnetwork 21 which the transfer apparatus 11 produces | generates. Explanatory drawing (1) of the link state information about the own apparatus which the transfer apparatus 11 produces | generates. Explanatory drawing (1) of the link state information about the own apparatus which the transfer apparatus 12 produces | generates. Explanatory drawing (1) of the link state information about the own apparatus which the transfer apparatus 13 produces | generates. Explanatory drawing (1) which shows the data transfer in a network. Explanatory drawing (2) of the link state information about the own apparatus which the transfer apparatus 13 produces | generates. Explanatory drawing (1) which shows data transfer when a failure generate | occur | produces in a broadcast network. Explanatory drawing of the link state information about the network which the transfer apparatus 12 produces | generates. Explanatory drawing (3) of the link state information about the own apparatus which the transfer apparatus 13 produces | generates. Explanatory drawing (1) which shows the data transfer in which the communication path switched when the failure generate | occur | produced in the broadcast network. Explanatory drawing (2) of the link state information about the own apparatus which the transfer apparatus 11 produces | generates. Explanatory drawing (2) of the link state information about the own apparatus which the transfer apparatus 12 produces | generates. Explanatory drawing (4) of the link state information about the own apparatus which the transfer apparatus 13 produces | generates. Network configuration diagram (2). Explanatory drawing (2) which shows the data transfer in a network. Explanatory drawing (2) which shows data transfer when a failure generate | occur | produces in a broadcast network. Explanatory drawing (2) which shows the data transfer in which the communication path switched when the failure generate | occur | produced in the broadcast network. The block diagram which shows the structure of a transfer apparatus. The block diagram which shows the internal block of the routing process part of a transfer apparatus. The operation | movement flowchart when a transfer apparatus receives the link state information about a network. The flowchart in case an own apparatus is selected as an alternative representative apparatus. The flowchart in case an own apparatus detects the failure of a representative apparatus and becomes a representative apparatus. Explanatory drawing of the link state information about a network. Explanatory drawing of the link state information about an own apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Transfer apparatus 12 Transfer apparatus 13 Transfer apparatus 14 Transfer apparatus 15 Transfer apparatus 21 Broadcast network 31 Link state information about network 32 Link state information about network 41 Protocol-specific information in link state information 51 Link state information about own apparatus 52 Link State Information About the Own Device 53 Link State Information About the Own Device 54 Link State Information About the Own Device 55 Link State Information About the Own Device 56 Link State Information About the Own Device 57 Link State Information About the Own Device 58 Own Link state information about the device 100 Control unit 101 CPU
DESCRIPTION OF SYMBOLS 102 Memory 103 Routing processing part 104 Routing table 110 Communication part 111 Transfer part 112 Network interface 113 Port 120 Reception processing part 121 Transmission processing part 122 Adjacency management part 123 Link state database 124 Path calculation part 125 Link state information generation part

Claims (10)

A communication system comprising a plurality of transfer devices connected to a network and using link states for routing,
The transfer device selected as the representative device generates the first network link state information about the network, and transmits the generated first network link state information.
The transfer device selected as the substitute representative device generates second link state information about the network, transmits the generated second network link state information,
The representative device, the substitute representative device, and one or a plurality of transfer devices other than the representative device or the substitute representative device are the first and second network devices generated by the substitute representative device and the representative device, respectively. Generate both device and link state information about the device, including both links to the link state information, and send the generated device and link state information.
One or a plurality of transfer devices other than the representative device or the substitute representative device hold the received first and second network link state information and a plurality of the device / link state information,
When the communication path between the representative device or the representative device and the network fails, one or a plurality of transfer devices other than the representative device or the alternative representative device receive the second network link state received from the alternative representative device. The communication system configured to maintain a link state information connection between transfer devices on the network excluding the representative device using a link to information. A transfer device in a communication system comprising a plurality of transfer devices connected to a network and using link states for routing,
When the transfer device is selected as a representative device, the transfer device generates first network link state information about the network, and transmits the generated first network link state information.
When the transfer device is selected as the substitute representative device, the transfer device generates second link state information about the network, and transmits the generated second network link state information.
The representative device, the substitute representative device, and one or a plurality of transfer devices other than the representative device or the substitute representative device are the first and second network devices generated by the substitute representative device and the representative device, respectively. Generate both device and link state information about the device, including both links to the link state information, and send the generated device and link state information.
One or a plurality of transfer devices other than the representative device or the substitute representative device hold the received first and second network link state information and a plurality of the device / link state information,
When the communication path between the representative device or the representative device and the network fails, one or a plurality of transfer devices other than the representative device or the alternative representative device receive the second network link state received from the alternative representative device. The transfer apparatus configured to maintain a link on link state information between transfer apparatuses on the network excluding the representative apparatus using a link to information.   The communication system according to claim 1, wherein the first and second network link state information for the network includes generated transfer device information and connected transfer device information. 2. The transfer device according to 2.   The communication apparatus according to claim 1 or 3, or the transfer apparatus according to claim 2, wherein the apparatus / link state information about the own apparatus includes the generated transfer apparatus information and link information.   2. The second network link state information generated by the alternative representative device includes information of a transfer device connected to the network, but does not include a representative device of the network. The communication system according to claim 3, or the transfer device according to claim 2.   The substitute representative device includes the second network link state information about the network including its own transfer device information and transfer device information connected to the network, but the representative device is connected to the network. 6. The communication system according to claim 1, wherein the second network link state information is distributed to other transfer apparatuses. Item 3. The transfer device according to Item 2.   When the transfer device other than the representative device deletes the first network link state information generated by the representative device and the representative device becomes unreachable, the second representative device generated by the alternative representative device The path calculation is performed using the network link state information, a path passing through the representative apparatus not included as a transfer apparatus connected to the network is invalidated and switched to an alternative path. The communication system according to claim 1 or 3, or the transfer apparatus according to claim 2. When a failure occurs between the representative device and the network and a transfer device other than the representative device and the alternative representative device detects the failure, the device / link state information about the own device generated by the transfer device Delete the link to the first network link state information generated by the representative device;
The transfer device maintains the reachability to the network by using the second network link state information, and after calculating the route in the transfer device, the transfer route passes through another transfer device other than the representative device. The communication system according to claim 1, or the transfer apparatus according to claim 2, wherein   The alternative representative device receives the deletion notification of the first network link state information received from the representative device when a failure occurs in the communication path between the representative device or the representative device and the network. The other transfer device switches communication via the representative device to another transfer device using the second network link state information generated by the alternative representative device. The communication system according to claim 1, or the transfer apparatus according to claim 2. When a failure occurs between the representative device and the network, and the alternative representative device detects it, the alternative representative device becomes the representative device for the network,
The alternative representative device notifies the other transfer device of the deletion notification of the first network link state information generated by the representative device,
When receiving the deletion notification, the other transfer device deletes the first network link state information generated by the representative device from the link state database, and the second network generated by the alternative representative device. The communication according to any one of claims 1, 3 to 6, characterized in that by using link state information, route calculation can be performed and a transfer device other than the representative device can be restored as a communication path. The transfer apparatus according to claim 2.

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